An auto iris of a camera lens is used to control the amount of entered light by adjusting a size of a hole between iris blades in the lens, and therefore it is implemented that a moderately exposed image is obtained in different lighting conditions.
Currently, a relatively commonly used auto-iris control method is mainly a direct current drive method, which controls opening and closing of an auto iris by controlling a size of an output direct current drive voltage. An existing direct current drive method may include presetting an initial drive voltage value, calculating a difference between current luminance and target luminance by collecting luminance/chrominance (Y/C) component data of an image, calculating a required direct current drive voltage according to the luminance difference, and adjusting the opening and closing of the auto iris.
However, disadvantages of an existing auto-iris control method lie in that there are many kinds of auto-iris lenses in the current market, and differences exist in parameters of auto-iris lenses of various models or brands, such as a direct current drive voltage, a damping factor of a coil of an iris, and an inertia coefficient of a blade of an iris. In the method in the prior art, it is difficult to implement automatic calibration of auto-iris lenses of different models or brands, and a person is usually required to participate in calibration of an iris control parameter. As a result, calibration of an auto iris requires relatively long time and relatively large human costs.
In addition, an iris drive control circuit is easily affected by factors such as an ambient temperature, a component characteristic difference, and an iris damping change; as a result, a static shift and dynamic drift occur in a direct current drive voltage of the iris, and then a manually calibrated parameter that is set at the time of delivery from the factory is invalid, thereby decreasing control precision. However, the method in the prior art cannot solve the foregoing problems of the static shift and dynamic drift of the iris drive control circuit.